Just thinking out loud here....so nothing has been tested yet.

By shimming the base of the intake lifters to increase lift (in proportion to the rocker ratio), the Cossie cams should increase lift from 11mm to 11,5mm.

Unlike on the STI’s where the lash clearance on the solid lifters is critical to prevent wear and damage, the hydraulics on the 4G63 heads should always allow for some tolerance on the clearance side once the oil pressure has set the rockers.

I’m curious as to what results on the dyno will show from the added shims and nothing else (both for stock cams and Cossie cams).

The marginal increase in raising the seat of the lifter should not hamper oil pressure on the channel of the lifter body, and since the pressure is released up and onto the lobe through the rocker cap, the shim has zero consequence.

If it works – and I think it may work, this will be of some value to those using stock cams who want higher lift on the intake and exhaust side.

 

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The hydraulic lifter would just compress 1mm more and give you no additional lift. The way to do something like this would be a higher ratio rocker arm. The stock rockers are approx a 1.7:1 ratio. I have installed custom 1.9:1 rockers in 3800 GM motors and it effectively makes the cams bigger. I dont know if anyone would make custom rockers for a 4G63.

Later

 

+1 I have seen this done on v8 motors as well

 

Well, if you were to shim it enough the plunger on the "lifter" would bottom out and you would start getting additional lift...problem is the valve would stay open all the time, so, nope bad idea.

 

the man speaks the truth. There are custom rockersetups out there. figure out where you wanna be cam wise too after this isdone, with the custom rocker setup you should prolly get custom grinds......lotta money and time involved in a project like that

 

A rocker ratio change would require a complete redesign of the cam profile. You'd need custom cams. HP/$ ratio= negative number. Forget it.

 

Cam switch is much easier.

 

you would essentially just be making the lifter make up for the shim...if it could. maybe not in the 4g63but you need some preload on the lifter so it is within its adjustment range. .....i see no benefit to this

 

cant shim our lifters to make more lift.